The oxidation of a Nd-Fe-B permanent magnet at 400°C: a SEM, microhardness and Mossbauer study

Author

Le Breton, Jean-Marie ; Teillet, Jacques ; McGuiness, Paul J. ; Edgley, Donald S. ; Harris, Roy

Author_Institution

Lab. de Magnetisme et Applications, CNRS, Mont-Saint-Aignan, France

Volume

28

Issue

5

fYear

1992

fDate

9/1/1992 12:00:00 AM

Firstpage

2157

Lastpage

2159

Abstract

Nd₁₆Fe₇₆B₈ sintered magnets were heated in an open furnace for times up to 29 days. The results of scanning electron microscope (SEM) observations, quantitative EDX/WDX analysis, microhardness measurements and Mossbauer spectroscopy were found to be consistent with the Nd₂Fe₁₄B phase having been disproportionated by oxygen entering via the surface or the cracks. The diffusion front between the oxidized region (oxygen amount~35 at.%) and the unaffected region was observed moving through the grains, indicating that at 400°C the corrosion behavior of the Nd₂Fe₁₄B phase is not intergranular in nature. This indicates that the corrosion resistance of Nd-Fe-B magnets at elevated temperatures could be enhanced by the presence of precipitates in the matrix

Keywords

Mossbauer effect; X-ray chemical analysis; boron alloys; corrosion; ferromagnetic properties of substances; hardness; iron alloys; neodymium alloys; oxidation; permanent magnets; scanning electron microscope examination of materials; 400 degC; Mossbauer spectroscopy; Nd₁₆Fe₇₆B₈ sintered magnets; Nd₂Fe₁₄B phase disproportionation; SEM; corrosion behavior; corrosion resistance; diffusion front; microhardness; open furnace; oxidation; permanent magnet; precipitates; quantitative EDX/WDX analysis; Corrosion; Furnaces; Iron; Magnetic analysis; Neodymium; Oxidation; Permanent magnets; Phase measurement; Scanning electron microscopy; Spectroscopy;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.179428

Filename

179428